/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//httpclient/src/java/org/apache/commons/httpclient/util/EncodingUtil.java,v 1.8 2004/05/13 04:01:22 mbecke Exp $
 * $Revision: 480424 $
 * $Date: 2006-11-29 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package org.apache.commons.httpclient.util;

import java.io.UnsupportedEncodingException;

import org.apache.commons.codec.net.URLCodec;
import org.apache.commons.httpclient.HttpClientError;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.logging.Log;

/**
 * The home for utility methods that handle various encoding tasks.
 * 
 * @author Michael Becke
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 * 
 * @since 2.0 final
 */
public class EncodingUtil {

	/** Default content encoding chatset */
	private static final String DEFAULT_CHARSET = "ISO-8859-1";

	/** Log object for this class. */
	// private static final Log LOG = LogFactory.getLog(EncodingUtil.class);

	/**
	 * Form-urlencoding routine.
	 * 
	 * The default encoding for all forms is
	 * `application/x-www-form-urlencoded'. A form data set is represented in
	 * this media type as follows:
	 * 
	 * The form field names and values are escaped: space characters are
	 * replaced by `+', and then reserved characters are escaped as per [URL];
	 * that is, non-alphanumeric characters are replaced by `%HH', a percent
	 * sign and two hexadecimal digits representing the ASCII code of the
	 * character. Line breaks, as in multi-line text field values, are
	 * represented as CR LF pairs, i.e. `%0D%0A'.
	 * 
	 * <p>
	 * if the given charset is not supported, ISO-8859-1 is used instead.
	 * </p>
	 * 
	 * @param pairs
	 *            the values to be encoded
	 * @param charset
	 *            the character set of pairs to be encoded
	 * 
	 * @return the urlencoded pairs
	 * 
	 * @since 2.0 final
	 */
	public static String formUrlEncode(NameValuePair[] pairs, String charset) {
		try {
			return doFormUrlEncode(pairs, charset);
		} catch (UnsupportedEncodingException e) {
			// LOG.error("Encoding not supported: " + charset);
			try {
				return doFormUrlEncode(pairs, DEFAULT_CHARSET);
			} catch (UnsupportedEncodingException fatal) {
				// Should never happen. ISO-8859-1 must be supported on all JVMs
				throw new HttpClientError("Encoding not supported: "
						+ DEFAULT_CHARSET);
			}
		}
	}

	/**
	 * Form-urlencoding routine.
	 * 
	 * The default encoding for all forms is
	 * `application/x-www-form-urlencoded'. A form data set is represented in
	 * this media type as follows:
	 * 
	 * The form field names and values are escaped: space characters are
	 * replaced by `+', and then reserved characters are escaped as per [URL];
	 * that is, non-alphanumeric characters are replaced by `%HH', a percent
	 * sign and two hexadecimal digits representing the ASCII code of the
	 * character. Line breaks, as in multi-line text field values, are
	 * represented as CR LF pairs, i.e. `%0D%0A'.
	 * 
	 * @param pairs
	 *            the values to be encoded
	 * @param charset
	 *            the character set of pairs to be encoded
	 * 
	 * @return the urlencoded pairs
	 * @throws UnsupportedEncodingException
	 *             if charset is not supported
	 * 
	 * @since 2.0 final
	 */
	private static String doFormUrlEncode(NameValuePair[] pairs, String charset)
			throws UnsupportedEncodingException {
		StringBuffer buf = new StringBuffer();
		for (int i = 0; i < pairs.length; i++) {
			URLCodec codec = new URLCodec();
			NameValuePair pair = pairs[i];
			if (pair.getName() != null) {
				if (i > 0) {
					buf.append("&");
				}
				buf.append(codec.encode(pair.getName(), charset));
				buf.append("=");
				if (pair.getValue() != null) {
					buf.append(codec.encode(pair.getValue(), charset));
				}
			}
		}
		return buf.toString();
	}

	/**
	 * Converts the byte array of HTTP content characters to a string. If the
	 * specified charset is not supported, default system encoding is used.
	 * 
	 * @param data
	 *            the byte array to be encoded
	 * @param offset
	 *            the index of the first byte to encode
	 * @param length
	 *            the number of bytes to encode
	 * @param charset
	 *            the desired character encoding
	 * @return The result of the conversion.
	 * 
	 * @since 3.0
	 */
	public static String getString(final byte[] data, int offset, int length,
			String charset) {

		if (data == null) {
			throw new IllegalArgumentException("Parameter may not be null");
		}

		if (charset == null || charset.length() == 0) {
			throw new IllegalArgumentException(
					"charset may not be null or empty");
		}

		try {
			return new String(data, offset, length, charset);
		} catch (UnsupportedEncodingException e) {

			// if (LOG.isWarnEnabled()) {
			// LOG.warn("Unsupported encoding: " + charset +
			// ". System encoding used");
			// }
			return new String(data, offset, length);
		}
	}

	/**
	 * Converts the byte array of HTTP content characters to a string. If the
	 * specified charset is not supported, default system encoding is used.
	 * 
	 * @param data
	 *            the byte array to be encoded
	 * @param charset
	 *            the desired character encoding
	 * @return The result of the conversion.
	 * 
	 * @since 3.0
	 */
	public static String getString(final byte[] data, String charset) {
		return getString(data, 0, data.length, charset);
	}

	/**
	 * Converts the specified string to a byte array. If the charset is not
	 * supported the default system charset is used.
	 * 
	 * @param data
	 *            the string to be encoded
	 * @param charset
	 *            the desired character encoding
	 * @return The resulting byte array.
	 * 
	 * @since 3.0
	 */
	public static byte[] getBytes(final String data, String charset) {

		if (data == null) {
			throw new IllegalArgumentException("data may not be null");
		}

		if (charset == null || charset.length() == 0) {
			throw new IllegalArgumentException(
					"charset may not be null or empty");
		}

		try {
			return data.getBytes(charset);
		} catch (UnsupportedEncodingException e) {

			// if (LOG.isWarnEnabled()) {
			// LOG.warn("Unsupported encoding: " + charset +
			// ". System encoding used.");
			// }

			return data.getBytes();
		}
	}

	/**
	 * Converts the specified string to byte array of ASCII characters.
	 * 
	 * @param data
	 *            the string to be encoded
	 * @return The string as a byte array.
	 * 
	 * @since 3.0
	 */
	public static byte[] getAsciiBytes(final String data) {

		if (data == null) {
			throw new IllegalArgumentException("Parameter may not be null");
		}

		try {
			return data.getBytes("US-ASCII");
		} catch (UnsupportedEncodingException e) {
			throw new HttpClientError("HttpClient requires ASCII support");
		}
	}

	/**
	 * Converts the byte array of ASCII characters to a string. This method is
	 * to be used when decoding content of HTTP elements (such as response
	 * headers)
	 * 
	 * @param data
	 *            the byte array to be encoded
	 * @param offset
	 *            the index of the first byte to encode
	 * @param length
	 *            the number of bytes to encode
	 * @return The string representation of the byte array
	 * 
	 * @since 3.0
	 */
	public static String getAsciiString(final byte[] data, int offset,
			int length) {

		if (data == null) {
			throw new IllegalArgumentException("Parameter may not be null");
		}

		try {
			return new String(data, offset, length, "US-ASCII");
		} catch (UnsupportedEncodingException e) {
			throw new HttpClientError("HttpClient requires ASCII support");
		}
	}

	/**
	 * Converts the byte array of ASCII characters to a string. This method is
	 * to be used when decoding content of HTTP elements (such as response
	 * headers)
	 * 
	 * @param data
	 *            the byte array to be encoded
	 * @return The string representation of the byte array
	 * 
	 * @since 3.0
	 */
	public static String getAsciiString(final byte[] data) {
		return getAsciiString(data, 0, data.length);
	}

	/**
	 * This class should not be instantiated.
	 */
	private EncodingUtil() {
	}

}
